Electrode for arc-lamps.



No. 700,495.- Patented May2l9-, .I902,

B.- HPFELT.

ELECTRUE FUR ARC LAMPS.

(Application led Feb. 24, 1902.)

(No Model.)

' f//J ATMP/vif? UNITED STATES PATENT EEICE.

- ROBERT HOPFELT, OF BERLIN, GERMANY.

ELECTRODE' FOR ARC-LAM PS.

SPECIFICATION' formingvpart of Letters Patent No. 700,495, dated May 20, 1902. Application tiled February 24, 1902. Serial No. 95,415. (No model.)

To all whoml it may concern,.- v

Beitknown that I, ROBERT HOPEELT, a subject of the Emperor of Germany, residing in Berlin, Germany, have invented an Improved Electrode for Arc-Lamps, of which the follow-v trodes will be as durable as or more durableA than carbon electrodes in use. This object I attain by covering the surface of the carbid electrodesrwith a layer impervious to moisture.

In the accompanying drawings, Figure l is -a longitudinal section, and Fig. 2 is a transverse section, of an electrode embodying my invention.

In` the figures, A indicates the body, and B the layer or envelop protecting the carbid from moisure. Such layer or envelop may consist of certain metals or of a thinl layer of varnish or cement orl of vitreous coatings,

` dac. Such a covering may be advantageously v produced by applying metal in the form of powder, metal salts, or metalloid salts with L an organic cement or like binding substance yimpervious layer.

to the electrodes and then burning them in a furnace'. By this burning process the binding substance is rst of all driven oit and then the metals or metal salts melt and cover thev electrodes at their su rface with a close-fitting The envelops which are employed with ordinary electrodes have quite v a different purpose, as these latter areintended merely to increase the conductibility or to color the light, so that the quality of keeping olf the moisture need not necessarily be present, while the envelops here described are for the purpose of protecting the carbid electrodes against the decomposing action of the moisture in the air. Protracted experiments have shown that this can also be eected by surrounding the electrodes with a protecting l metal envelop, which is advantageously drawn by mechanical means over the electrodes after g bid electrodes, as, in the first place, their melty ing-point is much too high, and, in the second place, such metals, particularly copperwith carbid, at the slightest entrance of moisture eiect an explosion of the acetylene developed, so that the electrodes burst apart. It is advantageous to employ only such metals as have a melting-point under 1,050 centigrade. The temperature which forms in the ,crater of the carbid electrodes is apparentlyso low that if, for example, iron or even copper or nickel were employed as a covering for carbid electrodes these absolutely would not melt, whereas these metals immediately evaporate when they are laid around carbon elec-` Apparently a much higher temperatrodes. ture is generated in this arc-flame than in the crater.

the completed production ot' the electrodesy It has been shown that tin, zinc, magnesium, brass, or,above,a1l, aluminium can be advantageously employed formy moisture- .protecting coating.

The destructive influence of the air on the carbid electrodes can also be guarded against by covering these electrodes with a thin layer of a varnish or a solid cement. The-solvent, as well as the organic constituents of the varnish, must be so constituted that the same do not produce a sooty llame in the light-arc, as the reiiector which is necessary for Auniform radiation of light would then become blackened and the intensity of the lightconsiderably diminished. Therefore thicki alcoholoids-for example, glycerin-may be advantageously employed, the carbid electrodes being dipped in glycerin or covered with a cement which is mixed with glycerin. ln the irst case the carbid is dissolved at the surface by the glycerin and converted'into .gas and lime. The mass of lime in consequence of the separation of the solvent then surrounds the carbid in such an impervious layer f that the moisture of theair is absolutely innocuous. The glyceri completely in the flame-arc with a bright flame without depositing even the slightest layer of soot.

If it is desired to cover the pieces of carbid with a cement, any metal oxids may be dissolved beforehand in glycerin, some carbon being advantageously mixed, so that the coating itself will become conductive of current. Such a coating hardens after a short time and also protects the carbid against moisture Without producing any injurious influences in the light While burning. Instead of glycerinot-her alcohols or alcoholoids can be employed.

Ifvarnishes or covering means of an organic nature-as, for instance, tar-be employed, it is advantageous to proceed in such manner that the electrodes (after saturation and advantageously after drying when using tar, for instance) are burned in order to change this organic substance into such solid carbon that the latter forms a sufcient means of keeping out air and moisture. If such a saturation,

with subsequent burning, is repeated sufficien tly often, the electrode can safely be covered with so close a layer of carbon that it may be brought into direct contact with even aqueous liquid.

I claim as my inventionl. As a new article of manufacture an arclamp electrode of carbid, having a coveringenvelop impervious to Water to protect the electrode against the decomposing action of the moisture of the air.

2. As a new article of manufacture, an arclamp electrode of carbid havinga solid metal envelop protecting the carbid from moisture, substantially as described.

3. As a new article of manufacture an arclamp carbid electrode having a protective envelop of aluminium.

In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses.

ROBERT HOPFELT.

Witnesses:

Anous;` Srnermsn Doesn, PAUL STAAL. 

